To reproduce:

guix build java-logback-classic

This is a dependency of maven.

Result:

starting phase `patch-generated-file-shebangs'
phase `patch-generated-file-shebangs' succeeded after 0.0 seconds
starting phase `build'
error: in phase 'build': uncaught exception:
wrong-type-arg #f "Wrong type (expecting ~A): ~S" ("string" #f) (#f) 
phase `build' failed after 0.0 seconds
Backtrace:
          19 (primitive-load "/gnu/store/7my17jqik49hmy3lwp4lrns09rv…")
In guix/build/gnu-build-system.scm:
    906:2 18 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . #)
In ice-9/boot-9.scm:
  1752:10 17 (with-exception-handler _ _ #:unwind? _ # _)
In srfi/srfi-1.scm:
    634:9 16 (for-each #<procedure 7ffff0b881c0 at guix/build/gnu-b…> …)
In ice-9/boot-9.scm:
  1752:10 15 (with-exception-handler _ _ #:unwind? _ # _)
In guix/build/gnu-build-system.scm:
   927:23 14 (_)
In ice-9/eval.scm:
    619:8 13 (_ #(#(#<directory (guile-user) 7ffff1fd3c80>) (# # …)))
    159:9 12 (_ #(#(#<directory (guile-user) 7ffff1fd3c80>) (# # …)))
    159:9 11 (_ #(#(#<directory (guile-user) 7ffff1fd3c80>) (# # …)))
    159:9 10 (_ #(#(#<directory (guile-user) 7ffff1fd3c80>) (# # …)))
In ice-9/boot-9.scm:
   222:29  9 (map1 ("java-logback-core" "java-slf4j-api" "java-co…" …))
   222:29  8 (map1 ("java-slf4j-api" "java-commons-compiler" "ser…" …))
   222:29  7 (map1 ("java-commons-compiler" "servlet" "groovy"))
   222:17  6 (map1 ("servlet" "groovy"))
In guix/build/utils.scm:
   491:10  5 (find-files #f _ #:stat _ #:directories? _ # _)
In ice-9/ftw.scm:
   447:23  4 (file-system-fold _ _ _ _ _ #<procedure 7ffff020a3a0 a…> …)
In ice-9/boot-9.scm:
  1747:15  3 (with-exception-handler #<procedure 7ffff02a03c0 at ic…> …)
In unknown file:
           2 (lstat #f)
In ice-9/boot-9.scm:
  1685:16  1 (raise-exception _ #:continuable? _)
  1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
Wrong type (expecting string): #f
builder for `/gnu/store/x2b3pwfmzb3clxnnpnq3ndd9sdzlz4j8-java-logback-classic-1.2.3.drv' failed with exit code 1
Erstellung von /gnu/store/x2b3pwfmzb3clxnnpnq3ndd9sdzlz4j8-java-logback-classic-1.2.3.drv fehlgeschlagen
Das Erstellungsprotokoll kann unter „/var/log/guix/drvs/x2/b3pwfmzb3clxnnpnq3ndd9sdzlz4j8-java-logback-classic-1.2.3.drv.gz“ eingesehen werden.
guix build: Fehler: build of `/gnu/store/x2b3pwfmzb3clxnnpnq3ndd9sdzlz4j8-java-logback-classic-1.2.3.drv' failed

Best wishes,
Arne